In-hospital cardiac arrest (IHCA) is a common event that is associated with poor patient outcomes. Yet, some hospitals have been consistently more successful in preventing and treating IHCA than others. While this is thought to be explained by the adoption of key strategies that improve care processes for IHCA, how these strategies are actually utilized in routine practice and the underlying factors contributing to their successful implementation remain largely unknown. Further, an integrative approach that examines strategies used during IHCA and those employed before and after these events has not been previously undertaken. This study will build on extensive prior work by our investigative team using the American Heart Association's Get With The Guidelines (GWTG)- Resuscitation registry and leverage our team's expertise in IHCA and qualitative research. The proposed HEROICA study will lay the foundation for future quality improvement efforts in IHCA by defining 'best practices' adopted by top-performing hospitals to address these events as well as potential barriers to their implementation. We will use a sequential mixed-methods approach to accomplish this goal, integrating quantitative and qualitative analyses. Its 3 Aims will: (1) identfy top- performing hospitals in preventing and treating IHCA within the GWTG-Resuscitation registry; (2) identify 'best practices' at the top-performing sites through semi-structured qualitative interviews; and (3) validate the practices associated with low IHCA incidence and high IHCA survival at top-performing sites. Findings from the study will be used to construct a toolkit of 'best practices' - the Code Blue Bundle. Upon successful completion of this research, we will partner closely with the American Heart Association (AHA) and the GWTG-Resuscitation registry to develop a national quality improvement program that will implement the Code Blue Bundle. Thus, the HEROICA study will increase the capacity of the NHLBI to improve outcomes for patients who suffer an IHCA by providing hospitals with practical and actionable strategies that can be implemented broadly to reduce the incidence and improve the survival of IHCA.